Abstract

Founder mutations in BRCA1 and BRCA2 have been reported in many different populations. We studied 105 Coloured and 16 Black Xhosa women residing in the Western Cape of South Africa diagnosed with breast cancer. We screened these patients using our standard panel of six previously reported SA Afrikaner and Ashkenazi Jewish BRCA1/2 mutations and identified only two Afrikaner mutations. Further screening by the protein truncation test (BRCA1 exon 11, and BRCA2 exons 10 and 11) revealed an additional four deleterious mutations (BRCA1 c.1504_ 1508del,p.Leu502AlafsX2, BRCA2 c.2826_2829del,p.Ile943LysfsX16, c.6447_6448dup,p.Lys2150IlefsX19 and c.5771_5774del,p.Ile1924Argfs X38). The latter, also known in Breast Cancer Information Core nomenclature as 5999del4, was identified in 4 of 105 (3.8%) Coloureds and 4 of 16 (25%) Xhosa women, which makes it a frequent founder mutation in the Western Cape Province. Although this mutation was previously reported to occur in the Netherlands, haplotype analysis indicated two distinct origins for the Dutch and South African mutations, excluding the possibility of a common Dutch ancestor and suggesting gene flow from the indigenous tribes such as the Xhosa to the Coloured population instead. Further studies to determine the carrier rate of this variant in the Xhosa and other SA populations are warranted.

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